Conventionally, in cataract and other surgery, a method has been adopted wherein a crystalline lens is extracted and removed through an incision made on ocular tissues such as the cornea (sclera) and anterior lens capsule, and thereafter, an intraocular lens is inserted into the eye via the above-mentioned incision to be set in the capsule in lieu of the removed lens.
Especially in recent years, the operation method using an insertion tool for intraocular lenses such as the one described in Patent Document 1 is commonly used. Generally speaking, the intraocular lens is inserted into the eye by means of inserting into the eye the tip opening of an insertion cylinder provided at the tip portion of the tool body through an incision and pushing out the intraocular lens stored in the placement part within the tool body in a compactly deformed condition from the tip opening of the insertion cylinder using an plunger inserted from the base portion of the tool body. Using this type of insertion tool allows an intraocular lens to be inserted without extending the incision formed to extract and remove the crystalline lens, thus saving the time and effort required for the surgical operation and reducing the risk of post-operative astigmatism and infections.
Examples of such an intraocular lens insertion tool include the one provided separately from the intraocular lens in which an individually packed intraocular lens is set up at the time of operation as well as the one provided with a preset intraocular lens. As to the so-called preset type intraocular lens insertion tool provided with a preset intraocular lens, it is to be packaged under sterilized conditions together with the intraocular lens and stored until the time of use.
Therefore, various mechanisms are proposed that can securely support the intraocular lens so as not to deform or damage the intraocular lens stored in the insertion tool for a long time. For example, Japanese Unexamined Patent Publication No. JP-A-2006-181269 (Patent Document 1) proposes to have a protection wall surrounding the intraocular lens project out from the placement part when the tool is not in use so as to prevent the intraocular lens from being subject to stress caused by malfunction of the plunger or the like, and get the protection wall detached when the tool is in use so that the intraocular lens is pushed out by the plunger.
However, even if such a mechanism for securely supporting the intraocular lens under storage is provided, it was sometimes hard to fully stabilize the behavior of the intraocular lens during insertion into the patient's capsule. In other words, the intraocular lens is composed of an optical part and a pair of support parts extending out from either side of the optical part, and these support parts are preset in the placement part so as to extend toward tip and rear ends of the tool body. Therefore, when pushing out the intraocular lens to the insertion cylinder by the plunger, there was a risk that the intraocular lens inserted into the capsule behaves differently, and in some cases, the support parts get damaged and so forth depending on how the front and rear support parts are warped or bent. Especially, in case of the so-called one-piece type intraocular lens wherein the optical part and support parts thereof are integrally formed with a soft synthetic resin material, the hardness of the support parts is subject to change with the temperature or the like, which makes it even harder to stabilize the position of the support parts.
Japanese Unexamined Patent Publication No. JP-A-2009-291399 (Patent Document 2) proposes a structure wherein the front support part abuts against a projection to be bent in a U-shape toward the optical part when the intraocular lens is pushed out by the plunger. This makes it harder for the front support part to move freely when being released from the insertion cylinder, which allows the intraocular lens to be inserted securely into the capsule. However, some intraocular lenses that are pushed out by the plunger in a deformed condition could not be bent in a desired shape without having the front support part engaged with a projection, depending on the hardness of the support part or the displaced preset conditions due to the transport. Also, even if such engagement is successful, there is a risk of not being able to obtain the desired U-shape depending on the hardness of the support part, and there still was a room for improvement in stably controlling the behavior of the support part of the intraocular lens.